The purpose of the proposed research is to compare olfactory and taste functioning in persons at risk for Alzheimer's disease (AD) with age- matched controls. Patient's with AD have losses in their ability to identify, recognize, and remember odorants. These losses are highly significant at the earliest stages of the disease. Decrements in the ability to detect odorants can also occur in early AD and become more severe as the disease progresses. To optimize early diagnosis of AD, this project prospectively studies a unique population at a higher risk of developing AD by virtue of a family history of confirmed AD. The losses in the sense of smell in AD occur in part because the histopathological changes characteristic of the disease are especially severe in those brain structures that process olfactory signals as well as the olfactory mucosa and the olfactory bulb. Pathological alterations in the olfactory and limbic structures of the temporal lobe produce decrements in the ability to identify, recognize, and remember odorants. Alterations close to the periphery produce losses in the ability to detect the presence of odorants. Four types of olfactory tests will be used to measure the ability to identify, recognize, remember, and detect odorants in order to assess whether any losses that are found result from temporal lobe or peripheral pathology. Taste measures will be obtained as a control for olfactory measures. Several major questions will be addressed. 1) Do persons at risk for AD differ as a group from age-matched controls in baseline measures of smell and taste performance at the beginning of the proposed longitudinal study? 2) Are persons with the poorest baseline measures of chemosensory functioning at greater risk for cognitive losses as determined incognitive proposal (Project 1) than persons with the best chemosensory functioning? 3) Is there a greater decline in chemosensory functioning from baseline during the study in persons at risk for AD than in age- matched controls? 4) Do individuals who exhibit chemosensory losses from baseline measures over the testing period have concomitant losses in cognitive functioning?